Some of them would like her land which will be sold to the highest bidder to be fair to all 15 nieces and nephews. They already have questioned how her money is spent and have tried getting their name on her checking account. I want to be prepared for trouble. I do not pay myself for taking care of all her needs as she may need her funds later so she can remain in her home.
Keep good records. If you buy something for her and reimburse yourself make as sure u keep receipts.
How is your Aunt doing? What are her health issues? Does she have memory problems?
As CountyMouse had mentioned in her post, when your Aunt passes on, your Power of Attorney is no longer in force. The person who takes over will be the Executor of your Aunt's Will. Hopefully your Aunt has a Will.
As for the Aunt's land, sounds like the cousins want to auction the land, is that correct? What if the highest bid is $5k for land that has a market value of $15k? Are the cousins 100% sure that the land will go to them? Some elders like to give assets to charity.
Please be sure everything you do is correct (not that I doubt it is) and is properly recorded. I think a visit to an attorney. at aunt's expense, would be wise. At that time you can look into a caregiver contract if you and aunt wish it. Some relatives get very greedy when they smell money and will go to great lengths and nasty behaviour to attempt to get it. They have no right to anything other than that which is according to aunt's decisions, Be sure her will is in order. Are you executor as well? Good luck!
But you will be in no way accountable for any instructions about her property that your aunt has put in a will; and it would be highly improper for you to attempt to influence her decisions about that. Has she in fact made a will?
There is nothing wrong with your cousins' asking reasonable questions about how your aunt's money is spent, and it might be quickest to give them reasonable answers. After all, they're her closest relatives too; I wouldn't assume they all have sinister motives. But this might also be a good time to spell out to them that she has appointed you to act for her and they must back off. What happened about the bank accounts? Did you ask the culprit to explain him/herself?
https://www.agingcare.com/articles/personal-care-agreements-compensate-family-caregivers-181562.htm
You are providing care that would otherwise have to paid for. In effect, you are preserving the value of the estate for your cousins.
If you really want to preserve the money for her future use, don't spend the money you are being paid. It will be your money and if you choose to spend it on her care when her money runs out, that's your choice.
Best of luck.